1. Technical Field
The present disclosure relates to image sensors and to methods of fabricating the same. More particularly, the present disclosure relates to rear light-receiving type image sensors, having improved optical sensitivity and to methods of fabricating the same.
2. Description of Related Art
In general, image sensors are semiconductor devices that convert incident light into an electrical signal. These image sensors may be roughly classified into charge coupled devices (CCDs) and complementary metal oxide semiconductor (CMOS) image sensors. Among them, the CMOS image sensors convert an electric charge into a voltage in each unit pixel, and output a signal from a signal line by a switching operation.
In general, the CMOS image sensors are each composed of a photo sensing part for sensing light and a CMOS logic circuit part for processing the sensed light into an electrical signal and converting the electrical signal into data. To enhance the photo sensitivity, an effort is being made to increase a percentage which an area of the photo sensing part accounts for of the total area of the image sensor. However, as the logic circuit part is not fundamentally removed, this effort has been subject to definite limitations.
Thus, additional efforts are being made to enhance the photo sensitivity of the above-mentioned CMOS image sensors. One of the efforts is a light collecting technique, which converts a path of the light incident on other regions than the photo sensing part and collects the light on the photo sensing part. Among them, one is designed to form a micro-lens on a color filter. However, this method of enhancing the photo sensitivity using the light collecting technique may nevertheless have a certain degree of limitations in enhancing the photo sensitivity as the image sensors are still more highly integrated.